Nonchattering alternating current solenoid and plunger



H. Y. FISHER 2,456,394 NONCHATTERING ALTERNLTING CURRENT SOLENOID AND PLUNGER Filed Nov. 23, 1945 Deca 14, 1948.

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' solenoids of the indicated generally by the character 22.

Patented Dec. 14, 1948 NONCHATTERING ALTERNATING CURRENT SOLENOID AND PLUNGER Hardin Y. Fisher, Hillside, m,

Manufacturing Corporation,

corporation of Illinois Application November-23, 1945, Serial No. 630,420

9 Glaims.

My invention relates to solenoids and is more particularly concerned with, but not limited to, type which are manufactured in large quantities by mass production methods.

One object of the invention is to provide a solenoid having improved operating characteristics.

The invention is especially directed to solenoids intended for operation by alternating current and another object is t ,erefore to provide such a solenoid with means adapted to insure quiet operation of the device by preventing vibration assignor to Soreng Chicago, 111., a

posing end portions 30 and 32. A plunger 34 is slidably mounted in this opening. The plunger of the plunger when it is held by the magnetic force at the limit of its working stroke.

In the new and improved solenoid to which this invention relates, when the plunger is drawn into the coil to its limiting position a part of the plunger is disposed between opposing end portions of the fixed frame with relatively slight clearance, and'it is an object of the invention to provide means for bringing one face of the plunger into actual contact with the adjacent and of the frame, together with means to prevent vibration or chattering of the plunger in this position.

More specifically, it is an object of the invention to provide a solenoid of the type just described with a shading coil located either in the end portion of the frame or in the adjacent portion of the plunger which contacts the frame as a means to prevent vibration of the plunger during such contact.

Other objects and advantages will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a longitudinal vertical sectional view of a solenoid embodying this invention, with parts in elevation; I

Fig. 2 is a top plan view of the plunger removed from its working position in the solenoid frame;

Fig. 3 is an end view partly in section taken as indicated at the line 3-3 on Fig. l;

is preferably formed of a multiplicity of strips It secured together by rivets 3t and 40. Two of the plunger strips 36a are made somewhat heavier than the remaining strips and have forwardly projecting end portions with holes 42 adapted to receive a pivot pin or other connecting means for attachment to a mechanism to be operated by the solenoid. Movement of the plunger 34 relative to the frame 20 is directed by a pair of guides 4!, each preferably formed of non-magnetic material in the shape of a shallow channel having top and bottom flanges 50, 50 which serve as rails between which the edges of the plunger are confined. The web portion 52 of the channel overlaps the frame 20 at its closed s ide and the rivet 22a serves to anchor the guide members 48 in posi- Fig. 4 is a fragmentary view partly in section showing a modification of the invention.

As shown in the drawings, the invention is applied to a solenoid which includes a generally rectangular frame 20 illustrated as being of laminated construction and formed of a multiplicity of similar layers of magnetic material secured together by rivets or other suitable fastening means The frame may have a pair of angle brackets 24 secured thereto by two of the rivets 22 .and each including a foot flange 26 with which any suitable fastening means may be engaged for mounting the solenoid on a support.

tion. The opposite ends of said guides 48 are disposed in the opening between the opposing end portions 30 and 32 of the frame 10 and are retained in position by means of strips which bridge the gap between the ends 30 and 32 at opposite faces of the frame 20, and are secured thereto by the rivets 22b. The channel-shaped cross section of the guides 48 is. seen in Fig. 3, and a fragment of one of the guides is shown in Fig. 1 as having a longitudinal slot 54 which receives one of the enlarged disc-like heads 40a of the rivet 40. One end 56 of the slot 54 in each of the guides v48 serves as a stop to engage the heads 40a of the rivet 4t and limit the outward movement of the plunger 34.

.The guides 48 are surrounded by an electrical coil 88 comprising many turns of wire carried by a spool 88 formed of any suitable insulating material. The coil 66 and its supporting spool 68 fit snugly in the opening of the rectangular frame 20 as seen in Fig. 1. when the coil 66 is energized and the plunger 34 is drawn into the frame 20, it is desirable to provide means for cushioning inward movement of the plunger as it approaches engagement with the rear wall of the frame 20. Accordingly, there is mounted on the end of the plunger 34 a bent plate of resilient material, and this plate is secured in place by a short length of metallic ribbon 82 which extends through slots in the projecting ends of the heavier plunger strips 360. The ends of the ribbon 82 are bent over as indicated in Fig. 1 toretain the ribbon spring plate 80 in position. The ends of the plate extend above and below the plunger 34 and contact the outer faces of the end portions 30 and 32 of the C-shaped frame as the plunger approaches its inner limit of movement.

The portion of the plunger which is then disposed between the opposing ends 30 and 32 of the frame is of greater height than the remainder of the plunger. the two heavier plates "a and the laminae 36 disposed between them being made somewhat wider at this point than the two outer plates b at each side of the plunger which run between the flanges 50, 50 of the guides 48. These higher portions 01 the upper and lower faces of the plunger 34 at its forward end are denoted by the numeral 31; they are of approximately the same length as the frame ends 30 and 22 and register therewith when the plunger is drawn fully into the frame as shown in Fig. 1. The extra magnetic material and the reduced air gaps thus provided in this portion of the magnetic circuit serve to reduce the reluctance of the circuit of the solenoid when the plunger is in this closed or rearward position.

Preferably, the extra height of the area 31 adjacent the end portion 30 of the frame is slightly more than the extra height of the area 31 opposite the end portion 32, so that as the plunger 34 approaches the limit of its inward movement into the frame 20, and the heightened areas 21 of the plunger register between the opposing ends so and 22 of the frame 20, the area 21 on the upper side of the plunger will be drawn into actual contact with the end of the frame. The running clearance in the guides 40 is sufficient to permit this contact.

Contact between the upper side of the plunger and the end portion of the frame is also assured by making one arm 80a of the spring ll stiffer than the other arm so plunger upward as it approaches the limit of its movement into the frame.

At the limit of its inward movement the inner end of the plunger engages the inner face of the C-shaped frame 20, and to prevent this pull from interfering with the lateral movement of the plunger for contact with the end portion 30, the inner end of the plunger is ground of! to form a surface which is not quite perpendicular to the axis of the plunger but is slightly oblique to the opposing face of the frame. This provides for initial contact between the frame and the plunger along the lower rear edge 34a and affords clearance at which allows the plunger to be tilted upwardly at its forward end, rocking about the bearing edge 34a. The engagement of the rivet heads 40a in the slots 54 of guides 48 will not interfere with this tilting movement, since, at this position of the plunger the heads 40a will be quite close to the fulcrum or bearing edge 34a.

If desired, this inner end of the plunger may be provided with a shading coil 10, fitted in slots 12, 12, to increase the holding force applied to the end of the plunger.

Now, with the upper face 31 of the plunger 34 initially engaged with the opposing end portion 30 of the frame, the alternating current which energizes the magnetic coil 66 would tend to cause vibration or chattering of the plunger against the frame. Therefore, a shading coil 90 is applied to this upstanding portion 31 of the plunger, as shown in Figs. 1, 2. and 3, it is a copper slug in the form of a closed loop lying in transverse grooves 92, 92, in the plates 38 and 36a, and staked or otherwise fixed therein. The

as to throw the i end portions of this coil 80 are of substantial the same thickness as the two plates 36b at eat side of the plunger and overlie them as seen Fig. 2. With the shading coil thus installed al Jacent the plane of contact of the plunger wit the end of the frame, the current induced in ti coil overcomes the tendency for vibration an permits the plunger to be held quietly and nrmi at this limitingposition until released by t! opening of the circuit or by reduction of th current strength supplied to the coil Bl.

Fig. 4 shows a modified arrangement of th invention in which theshading coil 80 is replace by a similar shading coil lllii inserted in slot I02 in the end portion 30 of the frame 20, wher it will operate in substantially the same manna as the coil 90 to eliminate vibration of the plunge in contact with this end of the frame.

With either arrangement, it will be evident tho although the plunger is held steadily against th: frame by the magnetic force generated by thi holding current, this force is at right angles t1 the pull of the plunger and to any retractivi de-energized; hence the use of the shading cot 90, or the shading coil I00, does not aflect the power of the solenoid but does materially improve its operation by eliminating vibration and consequent noise; and it does not interfere with prompt release, since any residual magnetic effect between the frame end 30 and the side of the plunger is perpendicular to the action of the spring or other retractive means employed to withdraw the plunger.

While there is shown and described herein certain structure embodying the invention, it is to be understood that the invention is not limited thereto or thereby and may assume various other forms and includes all modifications, variations, and equivalents coming within the scope of the following claims.

I claim:

1. A solenoid of the class described, comprising a generally c-shaped frame, an electrical coil located in said frame and having a central opening aligned with the opening between the ends of said frame, said electrical coil being adapted for conportion of increased height between the ends of said frame, said portion having upper and lower extremities of substantially the same area as the ends of said frame and being of such height as to provide air gaps between said extremities and the ends of said frame, said guides permitting limited lateral movement of said plunger, means biasing said upper extremity toward the adjacent end of the frame as the plunger moves inwardly through the opening, and a shading coil carried by the plunger in a plane adjacent the upper surface of said extremity.

2. A solenoid of the class described, comprising a generally c-shaped frame, an electrical coil lohaving a central opening between the ends of said frame, said electrical coil being adapted for con-- nection to a source of alternating current, a

plunger slidable in said openings, means for guid ing said plunger therein, said plunger having a portion of increased height between the ends of said frame, said portion having upper and lower extremities of substantially the same area as the ends of said frame and being of such height as to provide air gaps between said extremities and the ends of said frame, said guides permitting limited lateral movementof said plunger, the inner end of the plunger having a surface slightly ablique to the surface of the frame opposite said opening to provide a limited bearing for said end of the plunger against the frame upon which the outer end of the plunger can rock in said opening toward one end of the frame, means biasing said upper extremity toward the adjacent end of the frame as the plunger moves inwardly through the opening, and a shading coil carried bythe plunger in a plane adjacent the upper surface of said extremity.

4. A solenoid of the class described, comprising a generally C-shaped frame, an electrical coil located in said frame and having a central opening aligned with the opening between the ends of said frame, said electrical coil being adapted for connection to a source of alternating current, a plunger slidable in said openings. means for guiding said plungertherein, said plunger having a portion of increased height between the ends of said frame, said portion having upper and lower extremities of substantially the same area as the ends of said frame and being of such height as to provide air gaps between said extremities and the ends of said frame, said guides permitting limited lateral movement of said plunger, means biasing one of said extremities toward the adjacent end of the frame as the plunger moves inwardly through the opening, and a shading coil carried by the plunger in a plane adjacent the end surface of said extremity. 1

5. A solenoid of the class described, comprising a generally C-shaped frame, an electrical coil located in said frame and having a central opening aligned with the opening between the ends of said frame, said electrical co'il being adapted for connection to a source of alternating current, a plunger slidable in said openings, means for guiding said plunger therein, said Plunger having a portion of increased height between the ends of said frame, said portion of the plunger registering with the opposing end portions of the frame when the plunger reaches to limit of its inward movement through the opening, means biasing said portion of the plunger into contact with one end portion of the frame, and a shading coil carried by one of said contacting portions in a plane adjacent and. parallel to the plane of contact.

6. A solenoid of the class described, comprising a generally c-shaped frame, an electrical coil located in said frame and having a central opening aligned with the opening between the ends of said frame, said electrical coil being adapted for connection to a source of alternating current, a plunger slidable in said openings, means for guiding said plunger therein, said plunger having a portion of increased height between the ends of, said frame, said portion having upper and lower extremities disposed respectively opposite the ends of the frame when the plunger reaches the limit of its inward movement, means biasing said portion of the plunger toward one of said end portions of the frame and reducing the air gap between one of said extremities and the frame as compared with the air gap between the other extremity and the frame, and a shading coil carried by one of the parts in a plane closely adjacent the reduced air gap.

7. A solenoid of the class described, comprising a generally C-shaped frame, an electrical coil located in said frame and having a central opening aligned with the opening between the ends of said frame, said electrical coil being adapted for connection to a source of alternating current, a plunger slidable in said openings, means for guiding said plunger therein but permitting limited lateral movement of said plunger, means biasing a portionof the plunger into contact with one end portion of the frame as the plunger reaches its limit of inward movement through said openings, and a shading coil carried by one of said contacting portions in a plane adjacent and parallel to the plane of contact.

8. In a solenoid as defined in claim 7, said shading coil being carried by the plunger.

9. In a solenoid as defined in claim 7, said shading coil being carried by the end portion of the frame.

HARDIN Y. FISHER.

. REFERENCES CITED The following references are of record in the file of this patent:

- UNITED STATES PATENTS 2,304,553 Diebold Dec. 8, 1942 

